https://www.sevenforums.com/tutorials/106343-screen-saver-timeout-period-set-change.html

A) In regedit, navigate to the location below. (see screenshot below)

HKEY_CURRENT_USER\Software\Policies\Microsoft\Windows

B) In the left pane right click on Windows, and click on New and Key. (see screenshot above)
NOTE: If you already have the Control Panel key (step 3C), then skip this step and go to step 3D.

C) Type in Control Panel and press Enter. (see screenshot below)

D) Right click on Control Panel, and click on New and Key. (see screenshot above)
NOTE: If you already have the Desktop key (step 3E), then skip this step and go to step 3F.

E) Type in Desktop and press Enter. (see screenshot below)

F) In the right pane of Desktop, right click on a empty space and click on New and String Value. (see screenshot above)
NOTE: If you already have the ScreenSaveTimeOut string value (step 3G), then skip this step and go to step 3H.

G) Type in ScreenSaveTimeOut and press Enter. (see screenshot below)

H) In the right pane of Desktop, right click on ScreenSaveTimeOut and click on Modify. (see screenshot above)

I) Type in how many seconds (60 seconds = 1 minute) you want for how much user idle time must elapse before the screen saver is launched, then click on OK. (see screenshot below)